Distribution. Tobacco flea beetle, Epitrix hirtipennis (Melsheimer), is distributed widely in the United States. It is found most commonly in the southeast, but also as far north as Maryland and Michigan, and west to southern Colorado and California. It is infrequent in the northwest and Great Plains, but apparently occurs in Hawaii and Mexico. In Canada, it is known from Ontario and Quebec.
Southern tobacco flea beetle, Epitrix fasciata Blatch-ley, has limited distribution in the United States, and is known only along the Gulf Coast, from Florida to Texas. It occurs widely in Central America and the Caribbean, and as far south as Argentina.
Host Plants. Tobacco flea beetle adults feed readily upon tobacco and other plants in the family Solana-ceae, but sometimes attack other plants as well. Vegetable crops most frequently attacked are eggplant, potato, and tomato, but cabbage, cowpea, pepper, snap beans, and turnip are consumed occasionally. Weeds commonly serving as hosts are nightshade, Solanum spp.; jimsonweed, Datura stramonium; groundcherry, Physalis heterophylla; pokeweed, Phytolacca americana; burdock, Arctium minus; cocklebur, Xanthium spp.; and many others. The larvae develop successfully on many solanaceous plants, but do not survive on non-solanaceous plants. In studies conducted in Virginia, tobacco, potato, and jimsonweed were particularly good hosts for larvae (Glass, 1943).
The little information available on southern tobacco flea beetle suggests that the host range is nearly identical to that of tobacco flea beetle (White and Barber, 1974).
Natural Enemies. Tobacco flea beetle is preyed upon to a limited extent by general predators such as bigeyed bug, Geocoris punctipes (Say) (Hemiptera: Lygaeidae) (Dominick, 1943). The principal parasitoid seems to be Microctonus epitricis (Vierick) (Hymenop-tera: Braconidae), which causes parasitism rates of up to 25% (Dominick and Wene, 1941). This parasitoid also attacks southern tobacco flea beetle.
A nematode, Howardula dominicki Elsey (Nematoda: Allantonematidae), parasitizes up to 70% of larvae and 50% of adults of tobacco flea beetle. Host larvae are killed, and adult females are made sterile by the nematodes. Male beetles are important in nematode dissemination. The biology of this nematode was provided by Elsey and Pitts (1976), and Elsey (1977b,c).
Life Cycle and Description. The number of annual generations of tobacco flea beetle varies, with three reported from Kentucky, 3-4 in Virginia, and 4-5 from Florida. In Kentucky, Jewett (1926) observed first generation adults, resulting from reproduction by overwintering beetles, in mid-June. This was followed by a second generation in late July, and a third in September. Not all insects undergo the third generation, however, some commence overwintering after only two generations. In Florida, Chamberlin et al. (1924) reported four well-defined generations, but there may be additional generations. Overwintering occurs in the adult stage, under plant debris, and often in weedy or wooded areas adjacent to crop fields. In the south, the beetles may remain active throughout the winter.
Tobacco flea beetle, E. hirtipennis, and southern tobacco flea beetle, E. fasciata, are quite similar in appearance. E. hirtipennis is slightly larger and narrower, measuring 1.6-2.2 mm long and 1.9-2.0 times as long as wide. E. fasciata is 1.4-1.7 mm long and 1.7-1.8 times as long as wide. There is a broad transverse band across the elytra of both species, but although it is continuous in E. hirtipennis it is generally interrupted in E. fasciata (White and Barber, 1974).
The biology of the tobacco flea beetle was given by Metcalf and Underhill (1919), Jewett (1926), and Dominick (1943). Simple rearing techniques were pro-
vided by Jewett (1926), and Martin and Herzog (1987). Most research focuses on the relationship of tobacco flea beetle with tobacco, despite its common association with vegetable crops. The biology of southern tobacco flea beetle is poorly known, but is presumed similar to tobacco flea beetle. (See color figure 115.)
The nature of damage caused by these species is typical of flea beetle injury. Adults eat small holes partly or completely through the leaves, usually feeding from the underside. In the former instance, the adjacent remaining tissue usually dies and drops from the plant, leaving a somewhat circular hole. Foliage, especially of young plants, may be riddled with these small holes. In extreme cases, only the veins may remain, seriously disrupting the physiology of the plant. The result is usually stunted plants, although seedlings sometimes are killed. Feeding by as few as five beetles for a three-week period early in the life of a plant may result in significant yield reduction in tobacco, and presumably other crops (Semtner, 1984a). The beetles are more active and damaging during warm and sunny weather. They often feed selectively on shaded, or lower sections of the plant.
The larvae feed on the roots, particularly the rootlets. Even a single larva feeding on a germinating seedling may cause enough damage leading to death of the plant. The discoloration of the seedling stem base, wilting, and rapid death of the plant caused by larval feeding greatly resembles seedling "damping off'' due to plant parasitic fungi (Gentile and Stoner, 1968a).
Cultural Practices. Modification in planting date has been examined for reduction in flea beetle impact, but without much success. Late-planted crops may escape the attack of overwintering beetles, but plants then are relatively small and susceptible to injury by first brood adults (Semtner, 1984b). Also, crop yields or crop value are often adversely affected by late planting, which can outweigh the benefits of avoiding flea beetle injury.
Host-plant nutrition affects flea beetles differently, depending on the nutrient (Semtner et al., 1980). High nitrogen levels sometimes seem to affect flea beetles, but the pattern is not consistent. Plants with higher levels of phosphorus are less preferred by beetles, whereas higher levels of potassium favor adult abundance.
Among other methods of cultural control that have been studied are row covers, burning, and host plant resistance. Row covers work quite well for most pests, but as the beetles may overwinter in the ield, they can emerge under the protective covering. Thus, this practice has limitations if the ield was infested previously. Burning of crop residue and ield edges, where overwintering may occur, may kill some beetles, but it is no longer recommended routinely because the bene-its are slight. Host-plant resistance has been sought for some crops, such as Lycopersicon spp. (tomato and its relatives), but without much success (Gentile and Stoner, 1968b). Although some selections had glandular hairs that reduced feeding by adults, even wild species were susceptible to larvae.
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